Habitable Zone (artist’s impression)

Life as we know it depends on liquid water. This not-to-scale artist’s impression shows the small area around a star where liquid water can exist, the so called habitable zone. On planets closer to their parent star water evaporates, as shown on the inner of the three planets. If a planet is too far away from its star, the water on the surface gets frozen — as on the outer planet in this animation.